A comprehensive and internally consistent mineral dissolution rate database: Part I: Primary silicate minerals and glasses

Abstract

Mineral dissolution rates control the temporal evolution of many natural processes on the surface and upper crust of the Earth. This is the first of a series of papers describing the development and implementation of a comprehensive and internally consistent database of the dissolution rates of the major rock-forming minerals. In this paper, we describe the retrieval and regression of the dissolution rates of the primary rock-forming silicates, including quartz and other SiO2 polymorphs, feldspars, pyroxenes, amphiboles, micas, volcanic glass, and olivines. Owing to the limited fluid chemistry data available for many of the published experimental studies, BET surface area normalized mineral and most glass dissolution rates (r) were regressed usingr=∑iAiaH+nieEaiRT1−exp−AσRTwhere Ai stands for pre-exponential factors, aH+ corresponds to the hydrogen ion activity, ni refers to reaction orders, T designates absolute temperature, R denotes the gas constant, Eai represents activation energies, σ stands for Temkin's average stoichiometric number, and A denotes the chemical affinity of the dissolution reaction. Where relevant data were lacking, rates were extrapolated assuming that mineral dissolution follows similar trends within the same mineral group. Regression was performed using least-squares algorithms. The average difference between calculated and measured rates ranged from 0.1 to 0.7 log units depending on the mineral. The obtained rate equations were implemented into the carbfix.dat database for direct use in the PHREEQC software but can be extended to other geochemical modeling software, such as TOUGHREACT.